With ever increasing world population and greater industrialization of both the developed and undeveloped countries of the world, higher and higher demands for energy are being created. At the present time, these energy demands primarily are being met through the increased consumption of fossil fuels such as coal and petroleum. The world's supply of these and other expendable fuels, such as those used to produce atomic energy, is finite and non-replenishable. As a consequence, increased attention is being directed to alternative ways of producing energy on both large-scale and small-scale or individualized bases.
Substantial attention is being devoted to the development of solar energy and to the harnessing of the energy of the tides and winds. These sources of energy essentially are non-exhaustable. For this reason, as the available supplies of fossilized fuels are disappearing at an alarming rate, it finally is becoming clearly apparent that energy generation from sources which do not rely upon the consumption of finite resources must be developed in the relatively near future.
Wind plants, such as the familiar windmills used for many years in rural areas of the United States to pump water, and wind chargers for charging battery packs to supply electricity have generally fallen into disuse. Relatively little has been done to develop new forms of windmill blades or wind rotors for more efficiently harnessing the power available in the winds.
The common windmills and wind chargers use propeller or blade-driven rotors which rotate a horizontal shaft mounted high on a tower. If the wind charger is used to generate electricity, it is necessary also to mount the charger high on the tower to place it adjacent to the horizontal rotating shaft. The alternative is to provide some type of complex, cumbersome and energy wasteful linkage from the top of the tower to a location near the bottom. Such an alternative is impractical.
Another type of wind rotor used to rotate a vertical shaft has been known for many years. This type of rotor is essentially an S-shape vertical rotor known as a Savonious rotor. A Savonious rotor typically is built by splitting a cylinder equally through its length and offsetting the halves by a distance equal to or less than the radius of the cylinder. This assembly then is attached to a shaft through its center and rotates when it is exposed to the wind. Savonious rotors have not enjoyed much use, primarily due to the fact that they were introduced after the more common already perfected multi-blade farm windmill and the high-speed propeller-driven generators were in widespread use. Also, wind tunnel tests seemed to prove that conventional multi-blade farm windmills or propeller-driven generators were more efficient than the Savonious S-rotors.
Under normal outdoor operating conditions, however, a Savonious type rotor is superior in operation to the conventional blade type windmills. This is because of the characteristics of natural outdoor winds which differ significantly from wind tunnel operation. Two basic types of wind exist. First is the "prevalent" wind which is the prevailing wind in any given area and exists on most days. This wind also is, at any given time, a relatively steady wind both in magnitude and direction. The second type of wind is known as "energy" wind. Energy winds blow for much less time than prevalent winds but provide the highest percentage of power available for moving air masses over a measured period of time in any given locality.
Generally, energy winds exist in the form of gusts of wind which occur simultaneously with a prevalent wind. These gusts of energy winds, however, usually deviate in direction from the prevalent wind over a wide range, as much as 15 to 70 degrees. What this means to the efficient operation of any wind driven rotor or windmill readily becomes apparent when a conventional blade type rotor or propeller-driven unit is placed next to a Savonious-type rotor. During the times of operation in a steady wind, the wind tunnel results exhibiting superiority of the blade-type unit appear to exist. As soon as a gust occurs, however, the propeller or blade-driven unit swings into it under control of the vane which is provided for this purpose. Then as the gust of energy wind dies away, the vane of the blade-type windmill slowly moves the blade back into the prevalent wind. The Savonious S-rotor, in contrast, merely speeds up when a gust of wind occurs and slows down as the wind velocity drops back to the prevalent wind velocity. Analysis of this operation shows that the S-rotor is capable of handling wind sequentially or simultaneously from any direction and does not require any time to align itself first with the prevalent wind, then with a gust and back again, as contrasted with conventional blade windmill designs. This means an S-rotor can obtain the advantages of a significant percentage of the total available force of the winds, particularly from the power available in the gusts.
In addition to the ability of an S-rotor blade to absorb wind forces from all directions at all times, the same characteristics which permit this to occur also inherently provide improved durability of S-rotors over spinning propeller or fan-type windmills. A spinning blade, as is well known, exhibits a gyroscopic effect; so that its constant adjustment to the direction of wind gusts and the like under the control of the vane on the windmill subjects the windmill unit to substantial stresses, particularly at high wind speeds. No comparable stresses are incurred in the operation of an S-type rotor. In addition, an S-type rotor turns more slowly in a given wind; but because the S-rotor presents a much larger surface area to a moving air mass for a unit of a given diameter, it is capable of developing the same power as a faster rotating fan or propeller mill in spite of its lower rotational speeds.
Even with all of the advantages of Savonious S-rotors for producing energy from wind, there still are disadvantages in obtaining energy from relatively low prevalent winds, that is winds of the order of 5 to 7 miles per hour. In many areas of the country, however, the average or prevalent wind speed is this low, that is, 5 to 7 miles per hour. Therefore, it is desirable to provide an improved rotor which is capable of operation at low wind speeds with maximum efficiency and having the advantages of a Savonious S-type rotor design.